As Aguilera took the microphone to sing the deceased songstress' classic "At Last," she appeared to bend down and wipe her legs with the sleeve of her jacket.

As "The Voice" judge proceeded into a soulful rendition of the song, it became clear why. Sweating under the bright lights, lines of self tanner began to drip down her shins, leaving pronounced streaks.

Aguilera didn't seem too fazed by the tanner incident, though. After the performance, she tweeted, "One of the greatest moments of my life ... Singing with my idol, the legendary Etta James. You will be forever missed."

Aguilera posted a photo of herself with James, taken several years ago. And she gushed about the experience to People magazine.

"Not only did I have the incredible opportunity of meeting my idol, but to be asked by her family to perform at her memorial was so very touching and yet bitter sweet," she said. "Losing her was, to me, like losing a part of my soul."

James died on Jan. 20 at age 73 after a long battle with leukemia and dementia. Stevie Wonder also performed at her funeral, where Al Sharpton gave a eulogy and President Barack Obama provided a statement.